Dear Irvan,

In classical chemostat set-ups, the dilution rate is set by the experimenter. As long as other environmental parameters are constant and D < mumax (with Ks

Dear Jack,

Thanks for the answer. My feed is sorghum cane juice, which was used without equalization steps. The [Cs,in] is not fluctuating as often, but it does shift especially when new load of juice was introduced to feed storage tank, connected to the fermenter (only happened once in few days). I notice that at pre-set dilution rate, turbidity changes several hour after [Cs,in] shifts, while residual [Cs,out] is relatively constant. Do you think the cell growth rate could be influenced, or is that more of wash-out/ accumulation effect due to dilution rate? I plan to have constant turbidity in the fermenter, but no automatic control were available so I need to set proper dilution rate responding to different [Cs,in] manually (it's a makeshift fermenter!). The feed [Cs,in] is about 3 - 3.5 times of Ks. 

Dear Jack,

Thanks for the answer. My feed is sorghum cane juice, which was used without equalization steps. The [Cs,in] is not fluctuating as often, but it does shift especially when new load of juice was introduced to feed storage tank, connected to the fermenter (only happened once in few days). I notice that at pre-set dilution rate, turbidity changes several hour after [Cs,in] shifts, while residual [Cs,out] is relatively constant. Do you think the cell growth rate could be influenced, or is that more of wash-out/ accumulation effect due to dilution rate? I plan to have constant turbidity in the fermenter, but no automatic control were available so I need to set proper dilution rate responding to different [Cs,in] manually (it's a makeshift fermenter!). The feed [Cs,in] is about 3 - 3.5 times of Ks. 

Dear Irvan,

Thanks for the clarification. 

One important caveat is that Monod kinetics for growth always refer to the growth-limiting nutrient. How sure are you that, in the sorghum cane juice, sugar (sucrose or glucose?) is indeed the single growth-limiting nutrient?

In a substrate-limited chemostat set-up, a small change (step-up or step-down) of Cs,in will generally only cause a small and transient change in Cs,in (and, as long as Cs,in

Dear Jack,

Thanks for the answer. Good starting point to re-evaluate the process.

Dear  Irvan S. Kartawiria 

Please see chapter 5 “Growth Kinetics” from published book "Biochemical Engineering & Biotechnology" 2nd Edition Elsevier 2015.

You can find chapter 5 from below link.

Chapter Growth Kinetics

i run a batch fermentation in which i have to measure percentage of yeast using turbidometric method. the broth contains heterogenous population of cells. of which my aim is to  estimate only yeast cell s